1. Field of the Invention
The present invention relates to a slitting device to slit a material web into partial webs and a process for positioning a slitting device. The slitting device includes a knife arrangement that is movable transverse to a run direction of the material web. The knife arrangement includes a first knife attachment device positioned on one side of the material web and a second knife attachment device positioned on the other side of the material web. Further, the first knife attachment device includes a drive device with a positioning unit.
While the exemplary embodiments of the present invention describe the material web as a paper web, it is noted that other material webs, e.g., foils, may also be slit into partial webs utilizing the slitting device of the present invention.
2. Discussion of Background Information
Paper webs are often manufactured having widths that are too wide for a subsequent use or application. For this reason, the material webs are often slit, e.g., in one of the final processing steps, to a necessary or desired width. In this manner, many adjacently running partial webs may be formed from a single material web to be wound into many partial web rolls. Further, during the slitting of the material web, a straightening of the edges may be obtained.
Depending on the needs of the subsequent user of the paper webs, the partial webs generally have different and varying widths. Thus, a knife arrangement that is adjustable transversely to a run direction of the material web is preferred. The knife arrangement, if operating under a scissor-cut principle, generally includes two knife attachment devices, i.e., an upper knife and a lower knife. To ensure a clean cut, both knife attachment devices must be positioned precisely relative to one another. In the current state of the art, there are two acceptable possibilities to provide this positioning. First, the upper knife is connected mechanically to the lower knife during a new positioning. However, in this case, the material web may no longer be present between the two knife attachment devices, and both units are moved together in a coupled state into their new position, fixed there, and then decoupled from one another. Thus, this possibility requires a drive for each knife arrangement, a positioning unit, and a mechanical coupling device. Moreover, it is disadvantageous that an adjustment cannot be performed while the a paper web runs through the slitting device. Thus, this possibility does not allow for positioning of a second set of knife arrangements, e.g., to be utilized in a subsequent slitting process, while a material web is being slit. The ability to perform such an adjustment which would reduce set-up time.
In the second possible method, both knife arrangements are displaced independent of each other and positioned. Thus, while this method can be performed with a drawn-in paper web, each knife attachment device requires a drive and a positioning unit, i.e., a total of two drives and two positioning units. In addition to the increased industrial expenditure, the precision of the adjustment is sometimes decreased when utilizing this procedure because each knife attachment device is positioned relative to an individual point of reference, e.g., via counting angle increments moved by a wheel during the moving of the knife attachment devices. Length variations may arise between the rails of the upper and lower knife when utilizing this procedure if, e.g., the temperatures of both places are different, which certainly can occur during operation. Moreover, the combination of the drawbacks of both positioning units add up so as to diminish the exactness of positioning.